Fracturing gun



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D Nm L G US M N GU T Dec. 5, 1961 v. R. YoUNG ETAL FRACTURING GUN 2 Sheets-Sheet 2 Filed Nov. 6, 1958 INVENTORS.

N RA YOUNG JR.,

ST C. PITTMAN, JAMES E. BROADDUS,

EO MTH-Wx HW VF M ,.m|||||l..| z, Y .Il B W w F/ HAMMER ATTORNEY.

Unite States Patent hhce 3,011,551 Patented Dec. 5, 1961 3,011,551 FRACTURING GUN Vernon R. Young, Los Angeles, Calif., and Forrest C.

Pittman and James E. Broaddus, Duncan, Okla., as-

signors to Halliburton Company, a corporation of Delaware Filed Nov. 6, 1958, Ser. No. 772,203 2 Claims. (Cl. 166-55.1)

This invention relates to the fracturing of earth forma-l tions in oil wells `or the like and more particularly to an arrangement employing a gun for shooting bullets into the formation while hydraulic fracturing pressure is eX- erted upon it to assist in its initial breakdown.

The idea of shooting bullets into a formation during a hydraulic fracturing operation is not new. The present invention is directed to a particular arrangement for performing such an operation in a convenient manner.

In accordance with the invention, a gun is lowered into the well bore beneath a packer and apparatus is provided to utilize the sum of the hydrostatic head of the liquid column therein and the pump pressure exerted on the surface in performing the hydraulic fracturing to cause the gun to tire.

The objects of the invention will be apparent from the following description of the preferred embodiment of the arrangement for performing the functions described above.

In the drawings:

FIGURE 1 is a view in vertical cross section of a section of an oil well with the arrangement of the present invention being lowered therein;

FIGURE 2 is a View similar to FIGURE 1 but illustrating the position of the parts during the fracturing of a formation;

FIGURE 3 is a detailed vertical cross-sectional view of the gun used in the arrangement of FIGURE 1, and showing the position of the parts before the gun is tired.

FIGURE 4 is a view similar to FIGURE 3, but showing the position of the parts of the gun just after it is fired.

Referring to the drawing in detail and rst to the arrangement of FIGURE l, it will be seen that a well bore is there shown at 10. A casing 11 may be located in the well bore. Whether the well bore is cased or not is immaterial insofar as the present invention is concerned.

The arrangement of the present invention is lowered down through the casing 11 on a string of drill pipe or tubing 12. It includes a packer 13, a section or sub 14 of perforated pipe, couplings 1S and 16, the lower one of which is hollow .and provided with one or more inlet ports 17, a firing device 18, a gun 19 and a tail pipe 20.

When the assembly is being lowered into the well, the packer is, of course, retracted. When the desired location is reached, the packer is set as shown in FIGURE 2. In the arrangement shown, this is accomplished by merely lowering the supporting string 12. This compresses the packer longitudinally against the tail pipe 20. The packer may be of any known design, such as shown and described in the U.S. Patent to Morrisett No. 2,808,889. Y

As is readily apparent from FIGURE 1, the compression of this packer, resulting from the application of a longitudinal load to string 12 with tail pipe 20 resting on the bottom of the well bore, would laterally expand the packer into sealing engagement with the well bore. Any other known means may be employed for setting the packer, and any known type of packer may, of course, be used, and it may not be necessary to employ the tail pipe 20. Straddle packers may alsobe used to isolate the formation 21 to be fractured from the remainder of the well bore.

Referring now to FIGURES 3 and 4, it will be seen that the coupling 16 has a bore 22 extending therethrough, this bore being in connection with the ports 17.

The top of the bore 22 is closed by a plug -23 which also serves as a support for a breakable tension pin 24.y

'I'he tension pin is connected to a piston 25 located in the lower portion of the bore 22, and this piston has a fluid tight t with the bore, O-rings 26 or the like being provided to insure against leakage.

A piston rod 27 extends downwardly from the piston and connects it to a hammer 2S located in an air tightchamber 29 located in the coupling 30 which forms the top part of the gun 19. Atmospheric pressure, or atleast Y a low pressure, prevails in the'chamber 29v until the Vgun is red. n

The gun 19 is provided with a rfiring pin 31 suitably K mounted in the coupling beneath the hammer 28.

In accordance with conventional practice, the firing pin is adapted to strike a blank shell 32, which, in turn ignites prima cord 33 which leads to a behind `a bullet 3S'.

There may, of course, be a number of bullets fired by a single prima cord, or there may be a number of firing pins and a number ol prima cords employed to control the shooting of projectiles into the formation, but these detailedarrangements need not here be described since' they are well-known to those skilled in the art, being ir every day use. l Y

Also, it is within the purview of the invention, to use shaped charges instead of bullets to assist in fracturing' the formation.

The operation of the invention is as follows:

The assembly of FIGURE 1 is lowered into thewell bore until the gun is opposite the formation foibe frac-- tured. The packer 13 is then set, as shown in FIGUREZ, and hydraulic pressure applied to the portion of the Well bore beneath the packer by pumping fluid down through the string 12. 1

`vAs the pump at the surface is operated, fluid flows down through the string 12 and out into the portion of the well bore beneaththe packer through the perforations inthe pipe 14. Since the ports 17 are provided in the coupling 16, the arrangement is such that the piston 25 in the bore 22 is subjected to the sum of the hydraulic head and the pump pressure.

The tension pin 24 is so designed as not to break until some pre-determined pressure in the bore 22 above the piston 25 is reached. The conditions under which the formation is to be fractured are determined before the assembly is run into the well, so that the hydrostatic head can be determined, at least approximately, Iand an estimate made as to the break down hydraulic pressure on the formation. The tension pin 24 is designed for each particular job, so as to pull apart at a pressure which is wellv above that of the hydrostatic head of fluid in the well but less than the break down pressure of the formation.

Accordingly, as the pressure continues to build up in Y bullets or the like to assist in yfracturing an earth formation under the control of the hydraulic pressure of the fracturing uid itself. lA high hydraulic pressure is eX-; erted in the well bore before and during the ring operapowder charge 34 located Y tion. As the bullets are red, the fracturing fluid is forced under this hydraulic pressure into the formation, as roughly illustrated in FIGURE 2, but the shock of the ring increases the eiciency of the operation and tends to increase the fractured area. This is accomplished without any other operation than just placing the assembly at the required location, setting the packer and operating the pump in the usual manner. The bullets cannot fire until the desired high hydraulic pressure is reached.

While only one embodiment of the invention has been shown in the drawings, it is obvious that various changes may be made without departing from the spirit of the invention or the scope of the annexed claims.

We claim:

l. An apparatus lfor fracturing earth formations in a well bore comprising: a packer expandible into sealing engagement with the wall of said well bore, a conduit extending through said packer, iluid outlet means in said conduit communicating with said well bore below said packer, explosive, formation perforating means carried by said conduit below said packer, iluid pressure respon* sive detonating means for said perforating means sealed from said conduit interior and positioned below said packer, and fluid inlet means in iluid communication with said fluid outlet means through said well bore and providing fluid communication between said detonating means and said well bore whereby, upon said apparatus being positioned in a well bore and said packer being expanded into sealing engagement with said well bore, the well bore below the packer may be pressurized by supplying pressurized fluid to said conduit, the pressurized uid after entering said inlet means being eifective to actuate said detonating means to iire said explosive, formation perforating means thereby simultaneously imparting an explosive shock to said fluid and perforating Said well bore.

2. An apparatus for fracturing earth formations in a well bore comprising: a packer expandible into sealing engagement with the Wall of said well bore, a conduit extending through said packer, uid outlet means in said conduit communicating with said well bore below said packer, explosive, formation perforating means carried by said conduit below said packer, uid pressure responsive detonating means for said perforating means sealed from said conduit interior and positioned below said packer, land uid inlet means in fluid communication with said uid outlet means through said well bore and providimg fluid communication between said detonating means and said well bore, said detonating means including a firing pin, a hammer for striking said pin, hammer restraining `means 4releasable responsive tO the application of a predetermined stress, and piston means engaging said restraining means and in fluid communicat-ion with said inlet means, said piston means being axially movable to impose said predetermined stress on said rest-raining means in response to well bore pressure transmitted through said inlet means, whereby, upon said apparatus being positioned in a well bore and said packer being expanded into sealing engagement with said well bore, the well bore below the packer may be pressurized to provide sufficient fluid pressure which, in being transmitted to said piston through said means inlet, is effective to release said hammer restraining means so as to allow said hammer to strike said pin and detonate said explosive, formation perforating means, thereby simultaneously imparting an explosive shock to said fluid and perforating said well bore.

References Cited in the file of thisipatent UNITED STATES PATENTS OTHER REFERENCES Publication: New Fracturing Tool increases Injection Rate, World Oil, September 1957, page 136. (Copy in Div. 49.) 

